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</pre><pre class="rust ">
<span class="comment">// client_persistence.rs</span>
<span class="comment">// </span>
<span class="comment">// This file is part of the Eclipse Paho MQTT Rust Client library.</span>
<span class="comment">//</span>

<span class="comment">/*******************************************************************************
 * Copyright (c) 2017 Frank Pagliughi &lt;fpagliughi@mindspring.com&gt;
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Frank Pagliughi - initial implementation and documentation
 *******************************************************************************/</span>

<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">libc</span>;

<span class="kw">use</span> <span class="ident">std</span>::{<span class="ident">ptr</span>, <span class="ident">slice</span>, <span class="ident">mem</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ffi</span>::{<span class="ident">CString</span>, <span class="ident">CStr</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">os</span>::<span class="ident">raw</span>::{<span class="ident">c_void</span>, <span class="ident">c_char</span>, <span class="ident">c_int</span>};

<span class="kw">use</span> <span class="ident">ffi</span>;

<span class="kw">use</span> <span class="ident">errors</span>::{<span class="ident">MqttResult</span>, <span class="comment">/*MqttError,*/</span>};

<span class="comment">// TODO: Should we have a specific PersistenceResult/Error?</span>

<span class="kw">const</span> <span class="ident">PERSISTENCE_SUCCESS</span>: <span class="ident">c_int</span> <span class="op">=</span> <span class="ident">ffi</span>::<span class="ident">MQTTASYNC_SUCCESS</span> <span class="kw">as</span> <span class="ident">c_int</span>;
<span class="kw">const</span> <span class="ident">PERSISTENCE_ERROR</span>: <span class="ident">c_int</span> <span class="op">=</span> <span class="ident">ffi</span>::<span class="ident">MQTTCLIENT_PERSISTENCE_ERROR</span>;

<span class="doccomment">/**
 * Trait to implement custom persistence in the client.
 */</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">ClientPersistence</span> {
	<span class="doccomment">/**
	 * Open and initialize the persistent store.
	 * @param client_id The unique client identifier.
	 * @param server_uri The address of the server to which the client is 
	 *					 connected. 
	 */</span>
	<span class="kw">fn</span> <span class="ident">open</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">client_id</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>, <span class="ident">server_uri</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>) <span class="op">-&gt;</span> <span class="ident">MqttResult</span><span class="op">&lt;</span>()<span class="op">&gt;</span>;
	<span class="doccomment">/**
	 * Close the persistence store.
	 */</span>
	<span class="kw">fn</span> <span class="ident">close</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">MqttResult</span><span class="op">&lt;</span>()<span class="op">&gt;</span>;
	<span class="doccomment">/**
	 * Put data into the persistence store.
	 * @param key The key to the data.
	 * @param The data to place into the store.
	 */</span>
	<span class="kw">fn</span> <span class="ident">put</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">key</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>, <span class="ident">buffers</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw-2">&amp;</span>[<span class="ident">u8</span>]<span class="op">&gt;</span>) <span class="op">-&gt;</span> <span class="ident">MqttResult</span><span class="op">&lt;</span>()<span class="op">&gt;</span>;
	<span class="doccomment">/**
	 * Gets data from the persistence store.
	 * @param key They key for the desired data.
	 */</span>
	<span class="kw">fn</span> <span class="ident">get</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">key</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>) <span class="op">-&gt;</span> <span class="ident">MqttResult</span><span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">u8</span><span class="op">&gt;&gt;</span>;
	<span class="doccomment">/**
	 * Removes data for the specified key.
	 * @param key The key for the data to remove.
	 */</span>
	<span class="kw">fn</span> <span class="ident">remove</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">key</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>) <span class="op">-&gt;</span> <span class="ident">MqttResult</span><span class="op">&lt;</span>()<span class="op">&gt;</span>;
	<span class="doccomment">/**
	 * Gets the keys that are currently in the persistence store
	 */</span>
	<span class="kw">fn</span> <span class="ident">keys</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">MqttResult</span><span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">String</span><span class="op">&gt;&gt;</span>;
	<span class="doccomment">/**
	 * Clear the persistence store so that it no longer contains any data.
	 */</span>
	<span class="kw">fn</span> <span class="ident">clear</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">MqttResult</span><span class="op">&lt;</span>()<span class="op">&gt;</span>; 
	<span class="doccomment">/**
	 * Determines if the persistence store contains the key.
	 * @param key The key
	 * @return @em true if the key is found in the store, @em false otherwise.
	 */</span>
	<span class="kw">fn</span> <span class="ident">contains_key</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">key</span>: <span class="kw-2">&amp;</span><span class="ident">str</span>) <span class="op">-&gt;</span> <span class="ident">bool</span>;
}

<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">///</span>

<span class="doccomment">/**
 * An empty struct used to collect the persistence callback funtions from 
 * the C library.
 * These functions receive the persistence callbacks from the C library and
 * then pass them on to the user-supplied struct which implements the 
 * ClientPersistence trait.
 */</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ClientPersistenceBridge</span>;

<span class="kw">impl</span> <span class="ident">ClientPersistenceBridge</span>
{
	<span class="comment">// Callback from the C library to open the persistence store.</span>
	<span class="comment">// On entry, the &#39;context&#39; has the address of the user&#39;s persistence </span>
	<span class="comment">// object which is reassigned to the &#39;handle&#39;.</span>
	<span class="comment">// Subsequent calls have the object address as the handle.</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_open</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>,
									 <span class="ident">client_id</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">c_char</span>, 
									 <span class="ident">server_uri</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">c_char</span>,
									 <span class="ident">context</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_open&quot;</span>);
		<span class="kw">if</span> <span class="op">!</span><span class="ident">handle</span>.<span class="ident">is_null</span>() <span class="op">&amp;&amp;</span> <span class="op">!</span><span class="ident">client_id</span>.<span class="ident">is_null</span>() <span class="op">&amp;&amp;</span> <span class="op">!</span><span class="ident">server_uri</span>.<span class="ident">is_null</span>() <span class="op">&amp;&amp;</span> <span class="op">!</span><span class="ident">context</span>.<span class="ident">is_null</span>() {
			<span class="kw">let</span> <span class="ident">client_id</span> <span class="op">=</span> <span class="ident">CStr</span>::<span class="ident">from_ptr</span>(<span class="ident">client_id</span>).<span class="ident">to_str</span>().<span class="ident">unwrap</span>();
			<span class="kw">let</span> <span class="ident">server_uri</span> <span class="op">=</span> <span class="ident">CStr</span>::<span class="ident">from_ptr</span>(<span class="ident">server_uri</span>).<span class="ident">to_str</span>().<span class="ident">unwrap</span>();

			<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">context</span>);

			<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Ok</span>(_) <span class="op">=</span> <span class="ident">persist</span>.<span class="ident">open</span>(<span class="ident">client_id</span>, <span class="ident">server_uri</span>) {
				<span class="kw-2">*</span><span class="ident">handle</span> <span class="op">=</span> <span class="ident">context</span>;
				<span class="kw">return</span> <span class="ident">PERSISTENCE_SUCCESS</span>;
			}
		}
		<span class="ident">PERSISTENCE_ERROR</span>
	}

	<span class="comment">// Callback from the C library to close the persistence store.</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_close</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_close&quot;</span>);
		<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_null</span>() {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_ERROR</span>;
		}

		<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">handle</span>);

		<span class="kw">match</span> <span class="ident">persist</span>.<span class="ident">close</span>() {
			<span class="prelude-val">Ok</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_SUCCESS</span>,
			<span class="prelude-val">Err</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_ERROR</span>,
		}
	}

	<span class="comment">// Callback from the C library to add data to the persistence store</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_put</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>,
									<span class="ident">key</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>, 
									<span class="ident">bufcount</span>: <span class="ident">c_int</span>, 
									<span class="ident">buffers</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>, 
									<span class="ident">buflens</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_int</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_put&quot;</span>);
		<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">key</span>.<span class="ident">is_null</span>() <span class="op">||</span> 
				<span class="ident">buffers</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">buflens</span>.<span class="ident">is_null</span>() {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_ERROR</span>;
		}
		<span class="kw">if</span> <span class="ident">bufcount</span> <span class="op">==</span> <span class="number">0</span> {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_SUCCESS</span>;
		}
		<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">handle</span>);
		<span class="kw">let</span> <span class="ident">key</span> <span class="op">=</span> <span class="ident">CStr</span>::<span class="ident">from_ptr</span>(<span class="ident">key</span>).<span class="ident">to_str</span>().<span class="ident">unwrap</span>();

		<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bufs</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw-2">&amp;</span>[<span class="ident">u8</span>]<span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">new</span>();

		<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">bufcount</span> <span class="kw">as</span> <span class="ident">isize</span> {
			<span class="kw">let</span> <span class="ident">buf</span> <span class="op">=</span> <span class="ident">slice</span>::<span class="ident">from_raw_parts_mut</span>(<span class="kw-2">*</span><span class="ident">buffers</span>.<span class="ident">offset</span>(<span class="ident">i</span>) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>, 
												<span class="kw-2">*</span><span class="ident">buflens</span>.<span class="ident">offset</span>(<span class="ident">i</span>) <span class="kw">as</span> <span class="ident">usize</span>);
			<span class="ident">bufs</span>.<span class="ident">push</span>(<span class="ident">buf</span>);
		}
		<span class="kw">match</span> <span class="ident">persist</span>.<span class="ident">put</span>(<span class="ident">key</span>, <span class="ident">bufs</span>) {
			<span class="prelude-val">Ok</span>(_)  <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_SUCCESS</span>,
			<span class="prelude-val">Err</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_ERROR</span>,
		}
	}

	<span class="comment">// Callback from the C library to retrieve data from the </span>
	<span class="comment">// persistence store.</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_get</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>,
									<span class="ident">key</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>, 
									<span class="ident">buffer</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>, 
									<span class="ident">buflen</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_int</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_get&quot;</span>);
		<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">key</span>.<span class="ident">is_null</span>() <span class="op">||</span>
				<span class="ident">buffer</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">buflen</span>.<span class="ident">is_null</span>() {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_ERROR</span>;
		}
		<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">handle</span>);
		<span class="kw">let</span> <span class="ident">key</span> <span class="op">=</span> <span class="ident">CStr</span>::<span class="ident">from_ptr</span>(<span class="ident">key</span>).<span class="ident">to_str</span>().<span class="ident">unwrap</span>();

		<span class="kw">match</span> <span class="ident">persist</span>.<span class="ident">get</span>(<span class="ident">key</span>) {
			<span class="prelude-val">Ok</span>(<span class="ident">buf</span>) <span class="op">=&gt;</span> {	<span class="comment">// buf: Vec&lt;u8&gt;</span>
				<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="ident">buf</span>.<span class="ident">len</span>();
				<span class="kw">let</span> <span class="ident">cbuf</span> <span class="op">=</span> <span class="ident">libc</span>::<span class="ident">malloc</span>(<span class="ident">n</span>) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>;
				<span class="ident">ptr</span>::<span class="ident">copy</span>(<span class="ident">buf</span>.<span class="ident">as_ptr</span>(), <span class="ident">cbuf</span>, <span class="ident">n</span>);
				<span class="kw-2">*</span><span class="ident">buffer</span> <span class="op">=</span> <span class="ident">cbuf</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>;
				<span class="kw-2">*</span><span class="ident">buflen</span> <span class="op">=</span> <span class="ident">n</span> <span class="kw">as</span> <span class="ident">c_int</span>;
				<span class="ident">PERSISTENCE_SUCCESS</span>
			},
			<span class="prelude-val">Err</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_ERROR</span>,
		}
	}

	<span class="comment">// Callback from the C library to delete specific data from the </span>
	<span class="comment">// persistence store.</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_remove</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>,
									   <span class="ident">key</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_remove&quot;</span>);
		<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">key</span>.<span class="ident">is_null</span>() {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_ERROR</span>;
		}
		<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">handle</span>);
		<span class="kw">let</span> <span class="ident">key</span> <span class="op">=</span> <span class="ident">CStr</span>::<span class="ident">from_ptr</span>(<span class="ident">key</span>).<span class="ident">to_str</span>().<span class="ident">unwrap</span>();

		<span class="kw">match</span> <span class="ident">persist</span>.<span class="ident">remove</span>(<span class="ident">key</span>) {
			<span class="prelude-val">Ok</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_SUCCESS</span>,
			<span class="prelude-val">Err</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_ERROR</span>
		}
	}

	<span class="comment">// Callback from the C library to retrieve the set of keys from the</span>
	<span class="comment">// persistence store.</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_keys</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>,
									 <span class="ident">keys</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>,
									 <span class="ident">nkeys</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_int</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_keys&quot;</span>);
		<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">keys</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">nkeys</span>.<span class="ident">is_null</span>() {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_ERROR</span>;
		}

		<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">handle</span>);

		<span class="kw-2">*</span><span class="ident">keys</span> <span class="op">=</span> <span class="ident">ptr</span>::<span class="ident">null_mut</span>();
		<span class="kw-2">*</span><span class="ident">nkeys</span> <span class="op">=</span> <span class="number">0</span>;

		<span class="kw">match</span> <span class="ident">persist</span>.<span class="ident">keys</span>() {
			<span class="prelude-val">Ok</span>(<span class="ident">k</span>) <span class="op">=&gt;</span> {		<span class="comment">// k: Vec&lt;String&gt;</span>
				<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="ident">k</span>.<span class="ident">len</span>();
				<span class="kw">if</span> <span class="ident">n</span> <span class="op">!=</span> <span class="number">0</span> {
					<span class="comment">// TODO OPTIMIZE: This does a lot of copying</span>
					<span class="kw">let</span> <span class="ident">ckeys</span> <span class="op">=</span> <span class="ident">libc</span>::<span class="ident">malloc</span>(<span class="ident">n</span> <span class="op">*</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op">&lt;</span><span class="ident">usize</span><span class="op">&gt;</span>()) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>;
					<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">n</span> {
						<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">CString</span>::<span class="ident">new</span>(<span class="ident">k</span>[<span class="ident">i</span>].<span class="ident">clone</span>()).<span class="ident">unwrap</span>();
						<span class="kw">let</span> <span class="ident">sb</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">as_bytes_with_nul</span>();
						<span class="kw">let</span> <span class="ident">sn</span> <span class="op">=</span> <span class="ident">sb</span>.<span class="ident">len</span>();
						<span class="kw">let</span> <span class="ident">cbuf</span> <span class="op">=</span> <span class="ident">libc</span>::<span class="ident">malloc</span>(<span class="ident">sn</span>) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>;
						<span class="ident">ptr</span>::<span class="ident">copy</span>(<span class="ident">sb</span>.<span class="ident">as_ptr</span>(), <span class="ident">cbuf</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>, <span class="ident">sn</span>);

						<span class="kw-2">*</span><span class="ident">ckeys</span>.<span class="ident">offset</span>(<span class="ident">i</span> <span class="kw">as</span> <span class="ident">isize</span>) <span class="op">=</span> <span class="ident">cbuf</span>;
					}
					<span class="kw-2">*</span><span class="ident">keys</span> <span class="op">=</span> <span class="ident">ckeys</span>;
					<span class="kw-2">*</span><span class="ident">nkeys</span> <span class="op">=</span> <span class="ident">n</span> <span class="kw">as</span> <span class="ident">c_int</span>;
				}
				<span class="ident">PERSISTENCE_SUCCESS</span>
			},
			<span class="prelude-val">Err</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_ERROR</span>
		}
	}

	<span class="comment">// Callback from the C library to remove all the data from the </span>
	<span class="comment">// persistence store.</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_clear</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_clear&quot;</span>);
		<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_null</span>() {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_ERROR</span>;
		}
		<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">handle</span>);

		<span class="kw">match</span> <span class="ident">persist</span>.<span class="ident">clear</span>() {
			<span class="prelude-val">Ok</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_SUCCESS</span>,
			<span class="prelude-val">Err</span>(_) <span class="op">=&gt;</span> <span class="ident">PERSISTENCE_ERROR</span>,
		}
	}

	<span class="comment">// Callback from the C library to determine if the store contains </span>
	<span class="comment">// the specified key.</span>
	<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">extern</span> <span class="string">&quot;C&quot;</span> <span class="kw">fn</span> <span class="ident">on_contains_key</span>(<span class="ident">handle</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_void</span>,
											 <span class="ident">key</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">c_char</span>) <span class="op">-&gt;</span> <span class="ident">c_int</span> {
		<span class="macro">trace</span><span class="macro">!</span>(<span class="string">&quot;ClientPersistenceBridge::on_contains_key&quot;</span>);
		<span class="kw">if</span> <span class="ident">handle</span>.<span class="ident">is_null</span>() <span class="op">||</span> <span class="ident">key</span>.<span class="ident">is_null</span>() {
			<span class="kw">return</span> <span class="ident">PERSISTENCE_ERROR</span>;
		}
		<span class="kw">let</span> <span class="ident">persist</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">ClientPersistence</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">handle</span>);
		<span class="kw">let</span> <span class="ident">key</span> <span class="op">=</span> <span class="ident">CStr</span>::<span class="ident">from_ptr</span>(<span class="ident">key</span>).<span class="ident">to_str</span>().<span class="ident">unwrap</span>();

		<span class="kw">if</span> <span class="ident">persist</span>.<span class="ident">contains_key</span>(<span class="ident">key</span>) { <span class="number">1</span> } <span class="kw">else</span> { <span class="number">0</span> }
	}
}

<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">//								Unit Tests</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>

<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">tests</span> {
	<span class="comment">/*
	use super::*;
	//use std::ffi::{CStr};

	struct TestClientPersistence;

	impl ClientPersistence for TestClientPersistence {
		fn open(&amp;self, client_id: &amp;str, server_uri: &amp;str) -&gt; MqttResult&lt;()&gt; {
			Ok(())
		}

		fn close(&amp;self) -&gt; MqttResult&lt;()&gt; {
			Ok(())
		}

		fn clear(&amp;self) -&gt; MqttResult&lt;()&gt; {
			Ok(())
		}

		fn put(&amp;self, key: &amp;str, buffers: Vec&lt;&amp;[u8]&gt;) -&gt; MqttResult&lt;()&gt; {
			Ok(())
		}

		fn get(&amp;self, key: &amp;str) -&gt; MqttResult&lt;&amp;[u8]&gt; {
			let x = b&quot;Bubba&quot;;	//: &amp;&#39;static [u8] = &amp;&#39;static [ 0u8, 1u8, 2u8, 3u8 ];
			Ok(x)
		}

		fn remove(&amp;self, key: &amp;str) -&gt; MqttResult&lt;()&gt; {
			Ok(())
		}
	}

	#[test]
	fn test_new() {
		let tcp = TestClientPersistence {};
		let tcpp = Box::new(Box::new(tcp));
		let context = Box::into_raw(tcpp);

		let persist: &amp;mut Box&lt;ClientPersistence&gt; = unsafe { mem::transmute(context) };
		/*
		let persist: &amp;mut Box&lt;ClientPersistence&gt; = unsafe { mem::transmute(context) };
		let res = persist.open(&quot;clientid&quot;, &quot;tcp://localhost:1883&quot;);
		assert!(res.is_ok());
		*/

		let _ = unsafe { Box::from_raw(context) };
	}
	*/</span>
}

</pre>
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                    <dt>S</dt>
                    <dd>Focus the search field</dd>
                    <dt>&larrb;</dt>
                    <dd>Move up in search results</dd>
                    <dt>&rarrb;</dt>
                    <dd>Move down in search results</dd>
                    <dt>&#9166;</dt>
                    <dd>Go to active search result</dd>
                    <dt>+</dt>
                    <dd>Collapse/expand all sections</dd>
                </dl>
            </div>

            <div class="infos">
                <h2>Search Tricks</h2>

                <p>
                    Prefix searches with a type followed by a colon (e.g.
                    <code>fn:</code>) to restrict the search to a given type.
                </p>

                <p>
                    Accepted types are: <code>fn</code>, <code>mod</code>,
                    <code>struct</code>, <code>enum</code>,
                    <code>trait</code>, <code>type</code>, <code>macro</code>,
                    and <code>const</code>.
                </p>

                <p>
                    Search functions by type signature (e.g.
                    <code>vec -> usize</code> or <code>* -> vec</code>)
                </p>
            </div>
        </div>
    </aside>

    

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